The present invention is directed to an integrated optical multiplex-demultiplex module for bi-directional optical communication transmission. The module includes a laser diode and a strip waveguide for guiding the laser emissions to an out-coupling region being located on one surface of a substrate and a photodetector being arranged on an opposite surface of the substrate. The module has a grating arrangement which is frequency-selective and essentially does not influence the guided laser diode emissions of a first wavelength but it will influence radiation of a second wavelength which is different from the first wavelength which radiation is coupled into the in-coupling location from an external waveguide. The module also has a deflecting diffraction grating having grid lines proceding perpendicular relative to the propagation direction of the radiation in the strip or film waveguide and diffracts and guides the radiation having a second wavelength differing from the laser emissions to the detector on the opposite surface.
A multiplex-demultiplex module or muldex module which has a substrate with a laser diode and a strip waveguide on one surface and a photodetector on an opposite surface with the strip waveguide being provided with a frequency-selective grating for passing the emission of the laser diode and deflecting radiation of a wavelength different from the wavelength of the laser diode which has been coupling into the in-coupling location and having a second deflecting diffraction grating whose grid lines extend perpendicular to the propagation direction in the strip for diffracting the different wavelength onto the photo diode is disclosed in copending U.S. patent application, Ser. No. 812,468, filed Dec. 23, 1985, which U.S. application claims priority from earlier filed European application No. 85111386. In the module disclosed in the above mentioned U.S. application, the grid lines of the frequency-selective diffraction grating proceed obliquely relative to the propagation direction of the radiation guided in the strip waveguide leading from the laser diode to the in-coupling location. A radiation guided in this one waveguide and having a wavelength differing from the wavelength of the laser diode emissions is laterally coupled out of the waveguide by the frequency-selective grating into a second or additional strip waveguide which is arranged on the same side of the substrate and branches off from the one waveguide. The diverting diffraction grating is arranged on this additional waveguide. The grid lines of this second diffraction grating proceed perpendicular to the propagation direction of the radiation conducted in this waveguide. This second diffraction grating steers the radiation onto the photodetector which is the form of a photo diode. In the embodiment of the module, the photo diode is arranged on the side of the substrate lying opposite the one side on which the laser diode and the waveguide with the gratings are arranged. The diverting grating on the second waveguide is dimensioned such that the radiation coupled out by the frequency selective grating and guided in the additional waveguide is steered through the substrate onto the diode.
An integrated optical muldex module, wherein the laser diode, a film waveguide conducting the laser diode emissions to an in-coupling and out-coupling location and a photo diode are arranged on one side of a substrate is disclosed in an article by H. G. Unger, "Planar and Integrated Multi- and Demultiplexers" Proceedings of the 6th European Conference on Circuit Theory and Design, 6-8 September 1983, VDE-Verlag, Berlin, pages 387-389. A frequency-selective diffraction grating is arranged on the film or layer waveguide and this grating in contrast to the module of the type initially discussed guides the laser diode emission in the direction towards the out-coupling locations but does not influence a radiation supply from the in-coupling location and having a wavelength differing from the wavelength of the laser diode emission. The grid lines of the frequency-selective grating proceed obliquely relative to the propagation direction of the radiation and are also curved so that the divergent laser diode emission is convergent after the deflection by the grating. The photo diode appears as though they are arranged in the beam path of the radiation not influenced by the frequency-selective grating have a wavelength differing from the wavelength of the laser diode emisssion. The diffraction grating which steers this radiation to the diode does not seem to be present.